Plasma treatment - an increasing technology for paper restoration?

An important part of our cultural heritage consists of paper materials, which are stored in archives and libraries. Deterioration of written cultural relics is attributed to several causes, such as microbial contamination, oxidation, acidification, and others. It is therefore desirable to focus research activities on conservation and restoration techniques to develop appropriate treatments. A new technology in the field of restoration could be plasma treatment, which is a well-established technique in a number of other processes, such as plasma cleaning, etching and coating. The main aim of this project is the removal of microbial contamination combined with an increase in paper strength using a plasma-based treatment. Therefore, a special after-glow plasma reactor was constructed to enable careful paper treatment. Current experiments work with oxidising and reducing process-gases to treat naturally aged groundwood paper. A positive effect on the paper stability was achieved by varying treatment parameters, such as flow, pressure, power and time. An overall increase in paper stability of up to 20 % was possible. Parallel investigations using plasma treatment for microbial cleaning were carried out. Certain amounts of different fungi and bacteria were spread on naturally aged paper. After plasma treatment, the reduction in microorganisms was measured. This proved the fungicidal and bactericidal action of the after-glow plasma treatment. Nevertheless, optimisation with regard to different microorganisms and kinds of papers must be considered.